Simplify the following expression: $r = \dfrac{8}{2n} \div \dfrac{2}{10n}$
Answer: Dividing by an expression is the same as multiplying by its inverse. $r = \dfrac{8}{2n} \times \dfrac{10n}{2}$ When multiplying fractions, we multiply the numerators and the denominators. $r = \dfrac{ 8 \times 10n } { 2n \times 2}$ $r = \dfrac{80n}{4n}$ Simplify: $r = \dfrac{20}{1}$